Production of aqueous polymer compositions

ABSTRACT

Process for making organic solvent-free aqueous crosslinkable polymer composition comprising: a) preparing an aqueous solution of an acid-functional oligomer with Tg 10 to 125° C. and having crosslinker functional groups; b) conducting an aqueous emulsion polymerization to make an aqueous emulsion of an olefinic hydrophobic polymer in the presence of the aqueous oligomer solution, the hydrophobic polymer having Tg at least 25° C. below that of the oligomer and optionally crosslinker functional groups, and c) combining with a crosslinking agent reactable with the crosslinker groups of the oligomer and polymer, said composition having Koenig hardness of ≧40 sec and minimum film forming temperature (MFFT) ≦55° C. Also the aqueous composition so formed and its use in various applications. The aqueous composition has excellent properties and in particular an advantageous balance of MFFT and Koenig hardness.

This application is the national phase of international applicationPCT/IB95/00331, filed Apr. 27, 1995 which designated the U.S.

The present invention relates to a process for the production of certainaqueous crosslinkable polymer compositions useful for coating, to theaqueous compositions so produced, and to their use in coatingapplications.

There is an ever increasing impetus to replace or supplementsolvent-based polymer coating compositions with aqueous-basedcounterparts due to the environmental toxicity and flammability problemsposed by the use of volatile organic solvents. However, even whereaqueous-based polymer compositions have been devised, their productionhas usually entailed the intermediate use of organic solvents, requiringsubsequent removal which is costly and time-consuming, or theincorporation of a certain amount of a solvent in the final compositionwhich acts to ensure proper film-formation on coating (known as acoalescing solvent). There is therefore also now increasing pressure tosignificantly reduce or eliminate the volatile organic contents (VOC's)in aqueous-based polymer composition syntheses both as components intheir production (even if subsequently removed) and in the resultingcomposition as an aid to film coalescence.

Further still, even if one can achieve a solvent-free aqueous polymercoating composition, it has been found difficult to achieve one with abalance of good properties conventionally required in most coatingcompositions, particularly acceptably high hardness and low minimum filmforming temperature (MFFT). It should also have good water and solventresistance, and good storage stability.

We have now invented a process which enables such compositions to beprepared. In particular, the process of the invention produces in mostcases in the resulting composition an exceptionally advantageouscombination of MFFT and hardness wherein one obtains in a givencomposition an exceptionally high hardness opposite the particular MFFTof that composition.

According to the present invention there is provided a process for theproduction of an organic solvent-free aqueous crosslinkable polymercomposition useful for coating, which process is organic solvent-freeand comprises:

a) preparing an aqueous solution of an acid-functional oligomer builtfrom olefinically unsaturated monomers, said oligomer having a numberaverage molecular weight Mn within the range of from 500 to 50,000(preferably 2000 to 25000), a glass transition temperature Tg within therange of 10 to 125° C. (preferably 50 to 125° C.), said oligomer beingformed using an organic solvent-free aqueous emulsion or aqueoussolution polymerisation process, and said acid functionality renderingthe oligomer water-soluble per se or by neutralization, and saidoligomer also having functional groups for imparting crosslinkabilitywhen the aqueous polymer composition is subsequently dried,

b) conducting an aqueous emulsion polymerization process to form anaqueous emulsion of a hydrophobic polymer from at least one olefinicallyunsaturated monomer in the presence of the aqueous solution of theoligomer, said hydrophobic polymer having a Tg which is at least 25° C.lower than the Tg of said oligomer (preferably at least 40° C. lower),and said hydrophobic polymer optionally having functional groups forimparting crosslinkability when the aqueous polymer composition issubsequently dried, and

c) combining the aqueous emulsion from b) with a crosslinking agent byaddition of the crosslinking agent after the polymerisation of step b)and/or performing the polymerisation in the presence of the crosslinkingagent, said crosslinking agent being reactable with the crosslinkerfunctional groups of the oligomer and (if present) of the hydrophobicpolymer on subsequent drying to effect crosslinking, wherein saidcrosslinking agent is not an agent which effects crosslinking by theformation of ionic bonds,

and wherein further, said polymer composition on drying has a Koenighardness of at least 40 sec (preferably within the range 60 to 200 sec)and said polymer composition has a minimum film forming temperature of≦55° C. (preferably within the range 0 to 30° C.).

There is also provided an aqueous polymer composition which is formableby a process as defined supra.

There is further provided the use of an aqueous polymer composition asdefined supra in coating applications, and in particular in theprotective coating of substrates such as wood, plastics, metal andpaper.

The prior art discloses a number of processes in which an aqueousemulsion of a polymer system containing a low molecular weighthydrophilic polymer and a hydrophobic emulsion polymer has been producedby a multistage process and in which (often) the hydrophilic oligomerhas been solubilized in the aqueous medium.

U.S. Pat. No. 4,151,143 claims the production of surfactant-freeemulsion polymer coating compositions using a process which involves (1)a first stage wherein organic solution-prepared carboxyl-functionalpolymer is dispersed/solubilized in water by neutralization and (2) asecond stage wherein a mixture of polymerisable monomers is subjected toemulsion polymerisation. The first stage polymer can be of relativelylow molecular weight, the first and/or second stage polymer isoptionally hydroxy-functional and the emulsion can be optionally mixedwith an amino-type crosslinker such as hexamethoxymethyl melamine.

U.S. Pat. No. 4,894,394 concerns the production of an invertedcore/shell latex by (1) preparing a hydrophilic low molecular weightfirst stage polymer by aqueous emulsion polymerisation; (2) conducting asecond emulsion polymerisation to produce a hydrophobic second stage;and (3) adjusting the pH of the resulting inverted core-shell emulsionto dissolve the first stage. The first and second stage monomers canoptionally include hydroxyalkyl(meth)acrylates andglycidyl(meth)acrylate although no emphasis is laid on them.

U.S. Pat. No. 4,845,149 relates to an emulsion polymer preparation(useful as a pressure sensitive adhesive) by emulsion polymerisingmonomers in the presence of an aqueous solution or dispersion of acarboxyl functional support polymer (of low molecular weight).

U.S. Pat. No. 4,904,724 (≡EP 320865) discloses that an organic solventsolution polymer system (a blend of acid-functional and acid-freepolymers) is dispersed into water with neutralization and used as theseed for an aqueous emulsion polymerisation. The solution polymers canbe carbonyl functional in which case a crosslinker such as polyhydrazideis added.

CA 2,066,988 (≡DE 4,113,839) relates to emulsifier-free emulsionpolymerisation by polymerisation of ethylenic monomers (A) in an aqueousmedium containing a neutralised acid-containing polymer (B) (preferablywater-soluble styrene/acrylic acid copolymer of molecular weight1,000-5,000). The (A) monomers are fed to the aqueous medium duringpolymerisation and can optionally include amino or glycidyl functionalmonomers, although crosslinking per se is not mentioned.

EP 0,522,791 is concerned with redispersible polymer powders prepared bya 2-stage aqueous emulsion sequential polymerisation process to make acore/shell polymer emulsion, followed by optional spray drying. In thefirst stage a low molecular weight carboxy-functional polymer which canoptionally include up to 30% hydroxyalkyl(meth)acrylate is polymerisedin aqueous emulsion to form the shell part; this is neutralised, and inthe second stage, monomers, which can again optionally include up to 30%hydroxyalkyl ester, are polymerised to form the core part, and theaqueous emulsion of core/shell polymer optionally converted by spraydrying into a redispersible polymer powder. The core and shell arepreferably grafted together in the emulsion by the use of polyfunctionalcompounds such as allyl methacrylate. The disclosure is silent as to theuse of a crosslinking agent to effect curing after any coatingformation.

EP 0,587,333 is directed to water-resistant multi-stage polymer aqueousemulsions having an alkali-insoluble polymer and dissolvedalkali-soluble, acid-functional oligomer. They are made by sequentialaqueous emulsion polymerisation of a monomer system for the oligomer,including an acid functional monomer and optionally a polyfunctionalcompound, followed by that of a monomer system for the alkali-insolublepolymer optionally including an amine-functional monomer. The purpose ofthe polyfunctional compound, or the amine functionality of thealkali-insoluble polymer is to cause physical or chemical interactionbetween the alkali-soluble oligomer and alkali-insoluble polymer whilepresent in the emulsion, e.g. by grafting together of the two phaseswhile forming the final emulsion. Additionally, the aqueous emulsion canincorporate metal ions such as those of Zn, Mg, and Ca so as to createionic metal/carboxylate crosslinks, which would occur after coatingformation from the emulsion. The alkali-soluble oligomer is solubilizedin the emulsion either by neutralizing it with a base after completingboth polymerisation stages or, less preferably, by neutralizing it witha base before the commencement of the second stage polymerisation toform the alkali-insoluble polymer.

None of the above-discussed disclosures teaches a process having theselected combination of features and integers as defined in theinvention process which are utilised to produce a composition suitablefor coating having such an advantageous combination of properties asdiscussed above.

The process of the invention results in an aqueous composition providinga polymeric coating of high hardness (as defined) on substrates such aswood, plastics, metal and paper, the aqueous composition being of lowMFFT (as defined). It also achieves coatings of good solvent and waterresistance. The process itself is organic solvent-free, as is theresulting aqueous polymer composition. The composition also has goodshelf stability.

In particular, the process of-the present invention allows theproduction of compositions which for the most part have an exceptionallyadvantageous balance of MFFT and Koenig hardness wherein one obtains anunusually high Koenig hardness for the particular value of MFFT of thecomposition. This is most surprising because the achievement of low MFFTand high hardness in a composition would normally work against eachother, i.e. if the composition has a very low MFFT it will tend not tohave a particularly high hardness, or a very high hardness for thecomposition will not be commensurate with a relatively low MFFT.

Being aqueous-based, the lower limit of MFFT for invention compositionswill of course be the freezing point of the aqueous carrier phase. Thiswill usually be about 0° C. (perhaps slightly lower because of anydissolved constituent(s) although not usually below -2° C.). Thereforethe range of MFFT for the invention compositions will usually be about 0to 55° C., more usually 0 to 30° C. The Koenig hardness will be ≧40 secand more usually in the range 60 to 200 sec.

As discussed above, a particularly advantageous feature is that for mostcompositions of the invention, the combination of MFFT and Koenighardness is surprisingly exceptionally advantageous. We have in factfound that most compositions of the invention fit the followingempirical equation in terms of the relationship of MFFT and Koenighardness, where H represents Koenig hardness (in secs) and T representsMFFT (in °C.):

    H≧1.5T+70

So, e.g. when T=0° C.; H is ≧70 sec; when T is 5° C., H is ≧77.5 secs;when T is 10° C., H is ≧85° C. sec; when T is 20° C., H is ≧100° C.,when T is 40° C., H is ≧130° C. and so on.

Moreover, in many compositions of the invention, though not all, thecombination of MFFT and Koenig hardness is even more advantageous thansuggested above, and fits the empirical relationship:

    H≧1.5T+90

so e.g. when T is 0° C., H is ≧90 sec; when T is 10° C., H is ≧105 sec;when T is 40° C., H is ≧150 sec, and so on.

Not all compositions yielded by the invention process satisfy one orboth of these empirical equations, but most do, as is illustrated by theexamples (see later).

The solubilization of the oligomer is effected before carrying out thepolymerisation of step b). Solubilization subsequent to thepolymerisation to form the hydrophobic polymer, the preferred techniquein the process of EP 0,587,333 would incur a worse MFFT/Koenig hardnessbalance as compared to solubilization prior to making the hydrophobicpolymer.

Effecting grafting (or pre-crosslinking) during the formation of theemulsion composition, as described in EP 0,587,333 would likewise resultin an inferior balance of MFFT and Koenig hardness as compared toeffecting covalent crosslinking after coating formation, as is achievedwith the compositions of the invention.

Furthermore, providing ionic crosslinking after coating formation alsoas described in EP 0,587,333, would detract from the advantageousbalance of MFFT and Koenig hardness as achieved by the process of thepresent invention.

The process of the invention, including the stage of making theoligomer, is organic solvent-free, as is the resulting polymercomposition. While solvent-free usually means entirely solvent-free, itwill be appreciated that from a practical viewpoint it may sometimes bedifficult to exclude very small amounts of organic solvent(s), whichwould otherwise have no material effect on the process or composition,as e.g. when incorporating a small amount of a commercially-obtainedadditive which might be carried in a vehicle which is at least partly anorganic solvent(s). Therefore organic solvent-free is intended to alsoextend to substantially organic solvent-free.

In step a) of the process there is formed an aqueous solution of anoligomer of Mn 500 to 50,000 and built from the polymerisation ofolefinically unsaturated monomers. The polymerisation techniqueemployed, which is organic solvent-free, may in principle be an aqueoussolution polymerisation process to produce directly an aqueous solutionof the oligomer, but is more usually a conventional aqueous emulsionpolymerisation process to form an aqueous polymer emulsion or latex.Such a process is extremely well known and need not be described ingreat detail. Suffice to say that such a process involves dispersing themonomer(s) in an aqueous medium and conducting polymerisation using afree-radical initiator (normally water soluble) and (usually)appropriate heating (e.g. 30 to 120° C.) and agitation (stirring) beingemployed. The aqueous emulsion polymerisation can be effected withconventional emulsifying agents (surfactants) being used e.g. anionicand/or non-ionic emulsifiers such as Na, K and NH₄ salts ofdialkylsulphosuccinates, Na, K and NH₄ salts of sulphated oils, Na, Kand NH₄ salts of alkyl sulphonic acids, Na, K and NH₄ alkyl sulphatessuch as sodium lauryl sulphate, alkali metal salts of sulphonic acids.C₁₂₋₂₄ fatty alcohols, ethoxylated fatty acids and/or fatty amides, andNa, K and NH₄ salts of fatty acids such as Na stearate and Na oleate;aryl-containing analogues of the alkyl-containing surfactants are alsouseful; other surfactants include phosphates. The amount used ispreferably low, preferably 0.3 to 2% by weight, more usually 0.3 to 1%by weight based on the weight of total monomer(s) charged. Thepolymerisation can employ conventional free radical initiators e.g.hydrogen peroxide, t-butyl-hydroperoxide, cumene hydroperoxide,persulphates such as NH₄ persulphate, K persulphate and Na persulphate;redox systems may be used; combinations such as t-butyl hydroperoxideisoascorbic acid and FeEDTA are useful; the amount of initiator, orinitiator system, is generally 0.05 to 3% based on the weight of totalmonomers charged!. It will be appreciated that it is not necessary toemploy the entire amount of the oligomer prepared from thepolymerisation, or an aqueous solution of this entire amount, for theaqueous oligomer solution which is specified in steps a) and b) of theinvention process (although it can be if desired); only a portion of itneed be used for the purposes of steps a) and b)!.

The emulsion polymerisation process when used for step a) may be carriedout using an "all-in-one" batch process (i.e. a process in which all thecomponents to be employed are present in the polymerisation medium atthe start of polymerisation) or a semi-batch process in which one ormore of the components employed (usually at least one of the monomers),is wholly or partially fed to the polymerisation medium during thepolymerisation. Although not preferred, fully continuous processes couldalso be used in principle.

The polymerisation technique employed must of course be such that a lowmolecular polymer (as defined) is formed, e.g. by employing a chaintransfer agent such as one selected from mercaptans (thiols), certainhalohydrocarbons and a-methyl styrene, as is quite conventional. By anaqueous solution of the acid-functional oligomer is meant herein thatthe oligomer is either completely or substantially completely dissolvedin the aqueous medium so that it is present as a true (i.e. clear)solution or that some of the oligomer is dispersed in the aqueous mediumand some of it is dissolved therein (the term "water-soluble" beingsimilarly construed).

Thus, the acid-functional oligomer contains a sufficient concentrationof acid functionality to render the polymer partially or more preferablyfully soluble in aqueous media, if necessary by neutralization of acidgroups of the polymer, as would e.g. be achieved by adjustment of the pHof the aqueous medium. (If the acid-functional oligomer is onlypartially soluble in the aqueous medium of the emulsion, it will existtherein partly dispersed and partly dissolved). Usually, the medium inwhich the oligomer finds itself will be acidic (pH <7) and the acidgroups will be carboxyl groups so that dissolution will be effected byraising the pH of the medium (usually the aqueous polymerisation mediumin which the oligomer has been prepared) so as to neutralize the acidgroups by the addition of a base, such as an organic or inorganic base,examples of which include organic amines such as trialkylamines (e.g.triethylamine, tributylamine), morpholine and alkanolamines, andinorganic bases such as ammonia, NaOH, KOH, and LiOH. Of course, theaqueous medium containing the acid functional oligomer may already bealkaline (or sufficiently alkaline) such that the acid groups (such ascarboxyl groups) become neutralized without the requirement forpositively adding a base to raise pH, or the acid groups may be orinclude very strong acid groups such as sulphonic acid groups (pK 1 to2) so that neutralization may not be necessary to achieve dissolution.Further still, it is possible for acid monomers to be polymerised insalt form rather than as the free acid.

The aqueous emulsion polymerisation of step b) yields a hydrophobicemulsion polymer, this type of polymer being well understood by thoseskilled in the art. Generally speaking it may be considered herein as awater-insoluble polymer whose water-insolubility is maintainedthroughout the pH range. The hydrophobic nature of the polymer isachieved by virtue of the polymer containing a sufficient concentrationof at least one hydrophobic monomer (i.e. in polymerised form) to renderthe polymer hydrophobic and water-insoluble throughout the pH range.Thus the emulsion polymer formed in the emulsion polymerisation processof step b) is insoluble in the aqueous medium of that polymerisationprocess regardless of any adjustments in pH to which the medium could besubjected.

The monomer system used for the preparation of the acid functionaloligomer is any suitable combination of olefinically unsaturatedmonomers which is amenable to copolymerisation provided such a monomersystem includes an acid-bearing comonomer(s) (preferably in sufficientconcentration to render the resulting polymer fully or partially solublein aqueous media as discusses supra), or a comonomer(s) bearing anacid-forming group which yields, or is subsequently convertible to, suchan acid group (such as an anhydride, e.g. methacrylic anhydride ormaleic anhydride, or an acid chloride) and also a comonomer(s) whichimparts crosslinkability. Typically the acid-bearing comonomers arecarboxyl-functional acrylic monomers or other ethylenically unsaturatedcarboxyl bearing monomers such as acrylic acid, methacrylic acid,itaconic acid and fumaric acid. Sulphonic acid-bearing monomers couldalso e.g. be used, such as styrene p-sulphonic acid (or correspondinglystyrene p-sulphonyl chloride). An acid bearing monomer could bepolymerised as the free acid or as a salt, e.g. the NH₄ or alkali metalsalts of ethylmethacrylate-2-sulphonic acid or2-acrylamido-2-methylpropane sulphonic acid, or the corresponding freeacids. Other, non-acid functional non-crosslinking monomer(s) which maybe copolymerized with the acid monomer(s) include acrylate andmethacrylate esters and styrenes; also dienes such as 1,3-butadiene andisoprene, vinyl esters such as vinyl acetate, and vinyl alkanoates.Methacrylates include normal or branched alkyl esters of C1 to C12alcohols and methacrylic acid, such as methyl methacrylate, ethylmethacrylate, and n-butyl methacrylate, and (usually C5 to C12)cycloalkyl methacrylates acid such as isobornyl methacrylate andcyclohexyl methacrylate. Acrylates include normal and branched alkylesters of C1 to C12 alcohols and acrylic acid, such as methyl acrylate,ethyl acrylate, n-butyl acrylate, and 2-ethylhexyl acrylate, and(usually C5-C12) cycloalkyl acrylates such as isobornyl acrylate andcyclohexylacrylate. Styrenes include styrene itself and the varioussubstituted styrenes, such as α-methyl styrene and t-butyl styrene.Nitriles such as acrylonitrile and methacrylonitrile may also bepolymerised, as well as olefinically unsaturated halides such as vinylchloride, vinylidene chloride and vinyl fluoride. Functional monomerswhich impart crosslinkability (crosslinking monomers for short) includeepoxy (usually glycidyl) and hydroxyalkyl (usually C1-C12, e.g.hydroxyethyl)methacrylates and acrylates, as well as keto or aldehydefunctional monomers such as acrolein, methacrolein and vinyl methylketone, the acetoacetoxy esters of hydroxyalkyl (usually C1-C12)acrylates and methacrylates such as acetoacetoxyethyl methacrylate andacrylate, and also keto-containing amides such as diacetone acrylamide.The purpose of using such functional monomer is to provide subsequentcrosslinkability in the resulting polymer system as discussed. (Inprinciple the functional monomer used for imparting crosslinkabilitycould be acid-bearing monomer, but this is not usual).

Typically, the acid functional oligomer is derived from a monomer systemwhich contains 1-45 weight % of acid comonomer(s), preferably 3-30weight % and more preferably 3-20 weight %; 0.5 to 20 weight %,preferably 1 to 15 weight %, and particularly 1 to 10 weight % ofcrosslinking monomer(s); and 98.5-50 weight % of non acid functional,non-crosslinking comonomer(s), preferably 96-65 weight %, and morepreferably 96-75 weight %. The non acid functional, non-crosslinkingcomonomer(s) in some cases is usefully selected from one or more ofmethyl methacrylate, styrene, ethyl acrylate, n-butyl methacrylate andn-butyl acrylate while the acid monomer is for example methacrylic acidand/or acrylic acid. Useful oligomers of this type are derived from amonomer system which comprises 3-12 weight % methacrylic acid and/oracrylic acid, 1 to 10 weight % of diacetone acrylamide and/oracetoacetoxy ethylmethacrylate, 50-90 weight % methyl methacrylate, 0-30weight % of one or more of ethyl acrylate, n-butyl methacrylate andn-butyl methacrylate and 0-40 weight % styrene.

The oligomer from step a) should have a number average molecular weightwithin the range of from 500-50,000, preferably 2000-25,000 andparticularly 3,000-19,000. (Polymer molecular weights may be determinedby gel permeation chromatography calibrated using an appropriate knownpolymer as standard). The Tg of the oligomer should be in the range from10 to 125° C., more preferably 50 to 125° C., and particularly 70 to125° C.

The aqueous emulsion polymerisation process employed in step b) to formthe hydrophobic polymer, may, apart from the incorporation of the acidfunctional oligomer from step a), be that of a conventional aqueousemulsion polymerisation process and basically as described above whendiscussing the use of such a process for the preparation of theacid-functional oligomer. However, an important preferred feature of theinvention is that it is often possible to eliminate or much reduce therequirement for the addition of a surfactant to act as an emulsifier inthe polymerisation of step b), because the acid functional oligomeritself can fulfil such a function (i.e. act as an emulsifying agent).Thus the aqueous emulsion resulting from step b) preferably contains avery low level of such added emulsifier (not counting the oligomeritself), with usually less than 0.5% (preferably less than 0.25%, andoften zero) based on the total weight of monomers charged being used,and with the only surfactant present preferably being that remainingfrom the oligomer polymerisation (not counting the oligomer itself). Infact the overall level of surfactant (not counting the oligomer itself)is preferably <1% more preferably <0.5%, particularly <0.35%, based onthe total weight of monomers charged for the hydrophobic polymer.

The monomer system employed for the formation of the hydrophobic polymermust be such that the resulting polymer is hydrophobic as described.Similar non acid functional, non crosslinking monomers to those used formaking the oligomer may be employed, and in particular styrenes, such asstyrene itself, α-methlystyrene, o-, m- and p-methylstyrene, o-, m- andp-ethylstyrene, p-chlorostyrene and p-bromostyrene; normal and branchedacrylic and methacrylic esters of alkanols (usually 1-12C) andcycloalkanols (usually C5-C12) such as methyl methacrylate, ethylmethacrylate, n-butyl methacrylate, t-butyl methacrylate, 2-ethylhexylmethacrylate, isobornyl methacrylate, and cyclohexyl acrylate and thecorresponding acrylates; vinyl esters such as vinyl acetate and vinylalkanoates; vinyl halides such as vinyl chloride; vinylidene halidessuch as vinylidene chloride; dienes such as 1,3-butadiene andisoprene--but of course their selection must be such as to provide aresulting Tg which is at least 25° C. below that of the oligomer. Afunctional monomer(s) for imparting crosslinkability (which is notnormally an acid monomer) may optionally be included, examples of whichinclude hydroxy and epoxy functional (meth)acrylates such ashydroxyalkyl (usually C1-C12) methacrylate e.g. 2-hydroxyethylmethacrylate, glycidyl methacrylate, and the corresponding acrylates, aswell as keto- and aldehyde-functional monomers such as acrolein,methacrolein, and methyl vinyl ketone, acetoacetoxy esters ofhydroxyalkyl (usually C1-C12) acrylates and methacrylates such asacetoacetoxyethyl acrylate or methacrylate, and also keto oraldehyde-containing amides such as diacetone acrylamide.

Acid functional monomers could also be included as comonomers (e.g.acrylic or methacrylic acid), although at such a level (depending ontheir nature) as to not affect the hydrophobic character of theresulting polymer. Generally speaking, the monomer system used to makethe hydrophobic polymer will usually contain less than 5 weight % of anyacid-functional monomer(s) (no matter of what type), and preferably lessthan 2 weight %, and in some preferred embodiments none at all.

The hydrophobic polymer is in some cases usefully made from a monomersystem which comprises at least one of C₁₋₁₀ -alkyl methacrylate (suchas n-butyl methacrylate), and C₃₋₁₀ -alkyl acrylate (such as n-butylacrylate), and usually, diacetone acrylamide and/or acetoacetoxyethylmethacrylate.

The polymerisation to make the hydrophobic polymer could be carried outusing a chain transfer agent, but (unlike in the preparation of theoligomer) is usually effected without the use of such a material.

The number average molecular weight of the hydrophobic polymer isusually ≧50,000, more usually ≧100,000. The upper limit does not usuallyexceed 5,000,000.

The Tg of the hydrophobic polymer should be at least 25° C. below, morepreferably at least 40° C. below the Tg of the oligomer. Usually, the Tgof the hydrophobic polymer will be within the range of from -20° C. to50° C., more usually from 0° C. to 40° C.

The aqueous solution of the oligomer of step a) is present during theemulsion polymerisation of step b) to make the hydrophobic polymer.

The presence of the oligomer in the polymerisation of step b) can beeffected in various ways, with the following being exemplary.

In one embodiment the aqueous solution of the oligomer is admixed withall of the monomers to be used in the formation of the hydrophobicpolymer and an otherwise conventional "all-in-one" batch polymerisation(with no further addition of monomer(s)) is carried out to make thelatter.

In another embodiment, the polymerisation is basically still a batchone, with all of the oligomer solution being present in thepolymerisation vessel prior to the start of polymerisation with some ofthe monomer system for the hydrophobic polymer, with the remainder ofthe monomer system for the hydrophobic polymer being added quickly inone addition a while after the polymerisation has commenced.

In a further embodiment, the polymerisation is still basically a batchone, with all of the oligomer solution being present in thepolymerisation vessel prior to the start of the polymerisation, but themonomer system for the hydrophobic polymer is now split into severalequal parts (batches). These parts are added and polymerised consecutiveto one another in order to obtain more control over the polymerisation;therefore effectively it is a polybatch method.

In other embodiments, semi-batch processes are employed in which part(or none) of the monomer system for the hydrophobic polymer is presentprior to the start of polymerization in the polymerisation reactionvessel and part (or the entire amount) is fed to the reaction medium inthe polymerisation vessel during the course of polymerisation.

In one such embodiment, the aqueous oligomer solution is present (inpart) in the reaction medium for the polymerisation while part of theaqueous oligomer solution is mixed with the entire monomer system forthe hydrophobic polymer (acting as an emulsifier) and the latter fed tothe reaction medium in the polymerisation vessel during thepolymerisation.

In another embodiment, the entire oligomer solution is present in thereaction vessel prior to the start of polymerisation and the entiremonomer system for the hydrophobic polymer is fed to the vessel duringthe polymerisation, i.e. there is no oligomer present in the monomerfeed.

In a further embodiment, all of the aqueous oligomer solution is presentin the reaction vessel prior to the start of the polymerisation togetherwith part of the monomer system for the hydrophobic polymer, and theremainder of the monomer system fed during polymerisation (i.e. withoutoligomer in the feed).

In a still further embodiment part of the oligomer solution is presentin the reaction vessel prior to start of the polymerisation togetherwith part of the monomer system for the hydrophobic polymer, and theremainder of the monomer system admixed with the remainder of theoligomer solution is fed during polymerisation.

In at least some embodiments of the invention, it is believed that theaqueous emulsion produced after the formation of the hydrophobic polymermay be in the form of an "inverted core-shell" latex, in which thehydrophobic polymer has formed a core domain in the oligomer--witholigomer encapsulating the hydrophobic polymer particles or forming ashell round them, or carrying the hydrophobic polymer particles in itsswollen matrix. Alternatively, it may be more realistic to speak of theoligomer simply in terms of being a seed for the polymerisation processto form the hydrophobic polymer--irrespective of the actual structure ofthe resulting polymer system that is produced, of which we are notentirely certain. Accordingly, we do not wish to be bound by anyphysical structure which might be assumed or proposed for the resultingaqueous latex of the polymer system of the invention.

Preferably the amount of crosslinking agent in step c) that is employedis such that the ratio of the number of crosslinker groups present inthe oligomer and (if employed) in the hydrophobic polymer to the numberof reactive groups (for crosslinking purposes) in the crosslinking agentis within the range of from 10/1 to 1/3, preferably 2/1 to 1/1.5.

The crosslinker in step c) is usually combined with the aqueous emulsionfrom step b) by adding thereto after the polymerisation of step b)(sometimes just before use of the composition), although it may inprinciple also be combined by performing the polymerisation of step b)in the presence of the crosslinking agent, i.e. steps c) and b) becomecombined. A combination of both incorporation expedients may also inprinciple be used.

It is a preferred feature of the invention that the low molecular weightof the oligomer produced in step a) is achieved using a process which isother than that known to the art as catalytic chain transferpolymerisation, the use of which is not usual in the process of thisinvention although it may in principle be used. This process is thatwhere a low molecular weight polymer is produced using the technique ofradical polymerisation, using a free-radical initiator, in whichmolecular weight is controlled using a catalytic amount of a transitionmetal complex, and in particular a cobalt chelate complex, thistechnique being known in the art as a catalytic chain transfer (CCT)polymerisation. Such a technique has been described fairly extensivelyin the literature within the last decade or so. For example, variousliterature references, such as N. S. Enikolopyan et al, J. Polym. Sci.,Polym. Chem. Ed., Vol 19, 879 (1981), disclose the use of cobalt IIporphyrin complexes as chain transfer agents in free radicalpolymerisation, while U.S. Pat. No. 4,526,945 discloses the use ofdioxime complexes of cobalt II for such a purpose. Various otherpublications, e.g. U.S. Pat. No. 4,680,354, EP-A-0196783 andEP-A-0199436, describe the use of certain other types of cobalt IIchelates as chain transfer agents for the production of oligomers ofolefinically unsaturated monomers by free-radical polymerisation.WO-A-87/03605 on the other hand claims the use of certain cobalt IIIchelate complexes for such a purpose, as well as the use of certainchelate complexes of other metals such as iridium and rhenium. Finally,copending application PCT/GB94/01692 (publication WO-A-95/04767published Feb. 16, 1995) discloses a process for the preparation of anaqueous polymer emulsion which in one embodiment comprises a) preparingan aqueous solution of an acid-functional oligomer using a CCTpolymerisation process and b) conducting an aqueous emulsionpolymerisation to form a hydrophobic polymer in the presence of theoligomer solution. Both the oligomer and hydrophobic polymer mayoptionally include crosslinker groups and the composition can optionallyinclude a crosslinking agent. The disclosure does not discuss or teach aprocess having the selection of features and integers as defined in theinvention process. In particular, none of the example compositionsinclude an oligomer with crosslinker groups, and none have oligomerswith Tg within the range of 10-125° C. and which are also at least 25°C. higher than the Tg of the hydrophobic polymer.

It will be appreciated that the oligomer and optionally the hydrophobicpolymer possess functional groups for imparting latent crosslinkabilityto the composition (i.e. so that crosslinking takes place e.g. after theformation of a coating therefrom) when combined with the crosslinkingagent in step c). For example, one or both polymers could carryfunctional groups such as hydroxyl groups and the compositionsubsequently formulated in step c) with a crosslinking agent such as apolyisocyanate, melamine, or glycoluril; or the functional groups on oneor both polymers could include keto or aldehyde carbonyl groups and thesubsequently formulated crosslinker in step c) could be a polyamine orpolyhydrazide such as adipic acid dihydrazide, oxalic and dihydrazide,phthalic acid dihydrazide, terephthalic acid dihydrazide, isophoronediamine and 4,7-dioxadecane-1,10 diamine. It will be noted that suchcrosslinking agents will effect crosslinking with the functionalcrosslinker groups of the oligomer, and also the hydrophobic polymer ifpresent by virtue of forming covalent bonds, and are not crosslinkingagents which would effect crosslinking by virtue of the formation ofionic bonds, as e.g. by the addition of metal ions to react withpolymer-bound carboxylate ions.

The minimum film forming temperature (MFFT) of a composition as usedherein is the temperature where the composition forms a smooth andcrackfree coating or film using DIN 53787 and when applied using a SheenMFFT bar SS3000.

Koenig hardness as used herein is a standard measure of hardness, beinga determination of how the viscoelastic properties of a film formed fromthe composition slows down a swinging motion deforming the surface ofthe film, and is measured according to DIN 53157 NEN5319.

As is well known, the glass transition temperature of a polymer is thetemperature at which it changes from a glassy, brittle state to aplastic, rubbery state.

The solids content of an aqueous composition of the invention is usuallywithin the range of from about 20 to 65 wt % on a total weight basis,more usually 30 to 55 wt %. Solids content can, if desired, be adjustedby adding water or removing water (e.g. by distillation orultrafiltration).

The relative amounts of the oligomer and the hydrophobic polymer in theaqueous polymer composition are preferably such that the weight % of theoligomer, based on the weight of the oligomer plus the hydrophobicpolymer of the polymer composition, is preferably within the range offrom 1 to 70 weight %, more preferably 5 to 50 weight %.

The aqueous compositions of the invention may be used in variousapplications and for such purposes may be optionally further combined orformulated with other additives or components, such as defoamers,rheology control agents, thickeners, dispersing and stabilizing agents(usually surfactants), wetting agents, fillers, extenders, fungicides,bacteriocides, coalescing and wetting solvents (although solvents arenot normally required), plasticisers, anti-freeze agents, waxes andpigments.

The aqueous compositions may e.g. be used, appropriately formulated ifnecessary, for the provision of films, polishes, varnishes, lacquers,paints, inks and adhesives. However, they are particularly useful andsuitable for providing the basis of protective coatings for woodensubstrates (e.g. wooden floors), and plastics, paper and metalsubstrates.

The compositions once applied may be allowed to dry naturally at ambienttemperature, or the drying process may be accelerated by heat.Crosslinking can be developed by allowing to stand for a prolongedperiod at ambient temperature (several days) or by heating at anelevated temperature (e.g. 50° C.) for a much shorter period of time.

The present invention is now further illustrated, but in no way limited,by reference to the following examples. Unless otherwise specified allparts, percentages, and ratios are on a weight basis. The prefix Cbefore an example indicates that it is comparative.

The glass transition temperatures of oligomers in the examples were thevalues in °C. determined experimentally using differential scanningcalorimetry DSC, taking the peak of the derivative curve as Tg, orcalculated from the Fox equation (as for the hydrophobic polymers--seefollowing). Sometimes both methods were used and in such cases thevalues obtained were identical.

The glass transition temperatures of hydrophobic polymers in theexamples were calculated by means of the Fox equation. Thus the Tg, indegrees Kelvin, of a copolymer having "n" copolymerised comonomers isgiven by the weight fractions W of each comonomer type and the Tg's ofthe homopolymers (in degrees Kelvin) derived from each comonomeraccording to the equation: ##EQU1##

The calculated Tg in degrees Kelvin may be readily converted to °C. (Ifthe hydrophobic polymer is a homopolymer, its Tg is simply that of thepolymerised monomer--normally available from the literature). In twocases, the Tg's of the hydrophobic polymers were measured by DSC as wellas being calculated; the values obtained were virtually identical.

In the examples the following abbreviations are used:

    ______________________________________    MMA =    methyl methacrylate    DAAM =   diacetone acrylamide    AAEM =   acetoacetoxy ethyl methacrylate    MAA =    methacrylic acid    EA =     ethyl acrylate    AP =     ammonium persulphate    TM =     total monomer    s/s =    solids/solids    3MPA =   3-mercaptopropionic acid (chain transfer             agent)    LMKT =   dodecyl mercaptane (chain transfer agent)    SA =     stoichiometric amount    FM =     free monomer content    d =      dispersity (Mn/Mw when Mw = wt average mol             wt)    BMA =    n-butyl methacrylate    BA =     n-butyl acrylate    S =      styrene    DMEA =   dimethylethanolamie    t-BHPO = tert-butyl hydroperoxide    EDTA =   ethylenediamine tetraacetic acid    ADH =    adipic acid dihydrazide    ALMA =   allyl methacrylate    RT =     room temperature    ______________________________________

A typical recipe and procedure for the preparation of an aqueoussolution of an acid-functional oligomer for use in the invention processis as follows.

Recipe for Oligomer OL1

Composition EA/MMA/DAAM/MAA=12.08/73.32/8/6.6

Surfagene FAZ 109 V (phosphate emulsifying agent): 0.5% on TM (s/s). 25%In the reactor; 75% in the feed.

AP: 0.3% on TM (s/s). Added as a separate feed during emulsionpolymerisation (solids of the feed is 1.5% in dem. water).

LMKT: 4.5% on TM.

NaHCO₃ : 0.3% on TM. 67% In the reactor; 33% in the feed.

Neutralization: 2 SA NH₃.

Solids of the neutralised solution: 27%.

Logsheet and Procedure for the Preparation of the Oligomer OL1

    ______________________________________    Nr       Component         Amount (g)    ______________________________________    1        H.sub.2 O         910.75    2        Surfagene FAZ 109 V                               3.09    3        AP (1.5% (s/s) in demin. water)                               98.96    4        NaHCO.sub.3       1.0    5        H.sub.2 O         216.88    6        MMA               362.76    7        DAAM              39.58    8        MAA               32.66    9        EA                59.79    10       Surfagene FAZ 109 V                               9.28    11       NaHCO.sub.3       0.49    12       LMKT (dodecylmercaptane)                               22.27    13       NH.sub.3 (25%)    56.6    14       H.sub.2 O         56.6    15       H.sub.2 O         39.22    ______________________________________

Charge 1, 2 and 4 to the reactor. Heat the batch to 70° C. and add 5% ofthe preemulsified feed 5-12. Heat the batch to 80° C., add 30% of 3 andwait for 5 minutes. Start feeding the preemulsified feed 5-12 and theinitiator feed 3. The reaction temperature is 85±2° C. The monomer feedshould take 60 minutes; The initiator feed should take 70 minutes. Rinsethe feed tank with 15. Keep the batch at 85-90° C. for another 30minutes after the feed has been completed. The oligomer dispersion is awhite, low viscosity product. Cool down to 80° C. and add the solutionof 13 and 14 slowly. Keep at 80° C. for another 30 minutes. The oligomerdispersion will slowly change into a clear, low viscosity solution. Cooldown to 25° C.

Specifications

    ______________________________________    solids              27-28%    pH                  10    viscosity (mPas @ 25° C.)                        150    sediment before sieving (%)                        <0.2    sediment after sieving (%)                        0.05-0.1    FM (ppm)            <100 ppm (typical                        values: <10 ppm EA,                        35 ppm MMA, 115 ppm                        MAA    Tg (DSC) (°C.)                        75° C.    Mn                  4100    d                   2.3-2.4    ______________________________________

EXAMPLE 1

A typical recipe and procedure for the preparation of an inventioncomposition by the "preemulsified feed method" is as follows.

Recipe

Composition: Oligomer part: (see above for OL1) Polymer part:BMA/BA/DAAM=74.1/22.9/3 Tg (polymer part, calculated) (°C.): O

Oligomer/polymer (s/s): 60/100 (=37.5/62.5) 40% of the oligomer used inthe reactor: 60% of the oligomer is used to emulsify the monomer feed.

AP: 0.3% on TM (s/s). Added as a separate feed (2.5% solids). 0.2% on TMin the reactor.

Solids: 37%

Logsheet and Procedure for Composition of Ex 1

    ______________________________________    Nr.       Component      Amount (g)    ______________________________________    1         H.sub.2 O      94.33    2         Oligomer OL1 solution                             326.53    3         AP             0.75    4         H.sub.2 O      219.80    5         BMA            276.98    6         BA             85.42    7         DAAM           11.21    8         Oligomer OL1 solution                             489.79    9         DMEA           .37    10        H.sub.2 O      43.71    11        AP             1.12    12        H.sub.2 O      50.00    ______________________________________

Charge 1-3 to the reactor. Charge 4 and 8 to the feed tank. Mix for 5minutes. Add a mixture of 5-7 and 9 to the stirred solution of 4 and 8.Emulsify the feed. Add 10% of the preemulsified feed to the reactor.Heat the reactor to 85±2° C. Start feeding the preemulsified feed in 90minutes to the reactor. The initiator feed 10 and 11 should take 100minutes. Rinse the feedtank with 12. Keep the batch at 85±2° C. for 30minutes. Cool down to 40-45° C. Add 13.1 g of ADH (solid) to thedispersion (0.9 SA). Rinse with 20 g demin. water. Keep the batch at40-45° C. for 30 minutes. Cool down to RT.

Specifications

    ______________________________________    solids (%)       37-37.5%    pH               9.5    viscosity (mPas @ 25° C.)                     50    sediment before sieving (%)                     <0.2    sediment after sieving (%)                     0.05-0.1    FM (ppm)         <300 ppm (typical values                     <10 ppm EA, <25 ppm MMA,                     <125 ppm BA, <200 ppm BMA    MFFT (°C.)                     4    Koenig Hardness  76 sec    ______________________________________

EXAMPLE 2

Recipe

Composition: Oligomer part: (see above for OL1) Polymer part:BMA/BA/DAAM=74.1/22.9/3. Tg (polymer part, calculated) (°C.): O

Oligomer/polymer (s/s): 100/100 All oligomer in the reactor

AP: 0.5% on TM (s/s); 40% in the reactor, 60% as a separate feed (2.5%solids in demin. water)

Solids: 37%

Logsheet and Procedure for Composition of Example 2

    ______________________________________    Nr.       Component      Amount (g)    ______________________________________    1         H.sub.2 O      75.93    2         Oligomer OL1 solution                             900.19    3         AP             .49    4         BMA            180.26    5         BA             55.59    6         DAAM           7.29    7         H.sub.2 O      29.16    8         AP             0.73    9         H.sub.2 O      50.0    ______________________________________

Charge 1 to reactor and dissolve 3. Add 2. Charge 10% of the monomers4-6 to the reactor. Heat the batch to 85±2° C. Start feeding themonomers 4-6 and the initiator feed (8 dissolved in 7). The monomer feedshould take 60 minutes, the initiator feed should take 70 minutes. Rinsewith 9. Keep the batch at 85±2° C. for one hour. Cool down to 40±2° C.Add a solution of 11.55 g of ADH dissolved in 103.97 g of demin. water(0.7 SA). Keep the batch at 40±2° C. for 30 minutes.

Specifications

    ______________________________________    solids           37-37.5%    pH               9.5    viscosity (mPas @ 25° C.)                     60    sediment before sieving (%)                     0.2    sediment after sieving (%)                     0.1-0.2    FM (%)           <0.2    MFFT (°C.)                     0    Koenig Hardness  96 sec    ______________________________________

EXAMPLE 3

A typical recipe and procedure for the preparation of an inventioncomposition by a "batch method" is as follows:

Recipe

Composition: Oligomer part: (see above for OL1) Polymer part:BMA/BA/DAAM =74.1/22.9/3 Tg (polymer part, calculated) (°C.): O

Oligomer/polymer (s/s): 60/100 All oligomer in the reactor

Initiation system: 0.26% t-BHPO on TM (s/s) in the reactor 0.05%i-ascorbic acid on TM (s/s) in the reactor 5.07% FeEDTA on t-BHPO (s/s)in the reactor 0.21% i-ascorbic acid on TM (s/s) fed into the reactor

Solids: 35%

Logsheet and Procedure for Composition of Example 3

    ______________________________________    Nr.    Component            Amount (g)    ______________________________________    1      H.sub.2 O            231.11    2      Oligomer OL1 solution                                823.98    3      BMA                  138.06    4      BA                   42.58    5      DAAM                 5.59    6      DMEA                 0.19    7      t-BHPO (32.1% slurry in demin.water)                                1.51    8      FeEDTA (1% solution *)                                2.46    9      i-ascorbic acid (3.96% in demin. water)                                2.36    10     i-ascorbic acid (1.21% in demin. water)                                32.42    11     BMA                  138.06    12     BA                   42.58    13     DAAM                 5.59    14     DMEA                 0.19    15     t-BHPO (32.18% slurry in demin.water)                                1.51    16     FeEDTA (1% solution) 2.46    17     H.sub.2 O            202.44    18     i-ascorbic acid (3.96% in demin. water)                                2.36    19     i-ascorbic acid (1.21% in demin. water)                                32.42    ______________________________________     * Made from FeSO.sub.4, EDTA, NaOH and water.

Charge 1 and 2 to the reactor. Mix for 15 minutes. Add 3-6 to thereactor. Add 7 followed by 8. Heat the batch to 35° C. Keep the batch atthis temperature for 1 hour. Add 9. The temperature will rise to about57° C. Keep at peak temperature for 15 minutes. Start feeding 10. Thefeed should take 30 minutes. Let the temperature drift. Keep the batchat the reaction temperature for 15 minutes. Cool down to 35° C. Add11-14 to the reactor, followed by 15, 16 and 17. Keep the batch at 35°C. for 1 hour. Add 18. The temperature will rise to about 42° C. Keepthe batch at peak temperature for 15 minutes. Start feeding 19. The feedshould take 30 minutes. Let the temperature drift. Cool down to 40±2° C.Add 12.53 g ADH to the dispersion (0.9 SA). Rinse with 10 g demin.water. Keep the batch at 40±20° C. for 30 minutes. Cool down to roomtemperature.

Specifications

    ______________________________________    solids           35-35.5%    pH               9.5    viscosity (mPas @ 25° C.)                     80    sediment before sieving (%)                     <0.2    sediment after sieving (%)                     0.05-0.1    FM (%)           <0.2    MFFT (°C.)                     10    Koenig Hardness  84 sec    ______________________________________

A further acid-functional oligomer OL2 in aqueous solution was preparedas follows.

Recipe for Oligomer OL2

Composition MMA/MAA/DAM/BMA=36/8/8/48

soldium lauryl sulphate (emulsifying agent): 0.5% on TM (s/s). 25% inthe reactor; 75% in the feed. AP: 0.3% on TM (s/s). Added as a separatefeed during emulsion polymerisation (solids of the feed is 1.5% in dem.water).

LMKT and 3MPA: 2.4% on TM

Neutralization: 1 SA NH₃

solids of the neutralized solution: 27-28%

Logsheet and Procedure for the Preparation of the Oligomer OL2

    ______________________________________    Nr        Component      Amount (g)    ______________________________________    1         H.sub.2 O      876.5    2         SLS            2.0    3         AP (1.5% (s/s) in demin                             95.9              water    4         Water          207.1    5         SLS            6.0    6         LMKT           7.7    7         3MPA           3.8    8         MMA            172.7    9         MAA            38.4    10        DAAM           38.4    11        BMA            230.2    12        NH.sub.3 (25%) 60.7    13        H.sub.2 O      60.6    ______________________________________

1 and 2 are charged to the reactor. 4-11 are charged to the feedtank andpreemulsified by stirring. Heat the batch to 70° C. and add 5% of thepreemulsified feed to the reactor. Heat the batch to 80° C. and add 30%of 3. Wait 5 minutes and start feeding the remainder of thepreemulsified feed aver 60 minutes and simultaneously feed the remainderof 3 over 70 minutes at 85° C. Hold at 85° C. for 30 minutes and thenadd 12 and 13. Hold at 80° C. for another 20 minutes and cool to roomtemperature.

Specifications

    ______________________________________    solids                 27-28%    pH                     8.4    viscosity (mPas @ 25° C.)                           130    sediment               <0.1%    Tg (DSC, °C.)   60    Mn                     8,400    d                      2.5    ______________________________________

EXAMPLE 4

An invention composition was prepared using a 2-step polybatch method asfollows:

Recipe

Composition: Oligomer part: (see above for OL2) Polymer part:MMA/BA/DAAM=38/58/4 Tg polymer part, calculated (°C.)=0

oligomer/polymer (s/s): 100/100

All oligomer in the reactor

Initiator system 0:26% t-BHPO on TM (s/s) in the reactor. 0.05%i-ascorbic acid on TM (s/s) in the reactor. 5.07% FeEDTA on t-BHPO (S/S)in the reactor. 0.21% i-ascorbic acid on TM (s/s) fed into the reactor.

solids: ca. 35%.

Logsheet and Procedure for Composition of Ex 4

    ______________________________________    Nr       Component        Amount (g)    ______________________________________    1        Water            16.3    2        oligomer OL2 solution                              972.4    3        MMA              92.4    4        BA               141.0    5        DAAM             9.7    6        tBHPO (30% slurry in demin.                              2.1             water    7        Fe EDTA (1% solution*)                              3.16    8        i-ascorbic acid 1% in demin.                              12.2             water    9        i-ascorbic acid 1% in demin.                              51.1             water    10       Water            10    11       ADH              13.4    ______________________________________     (* see Example 3).

Charge 1 and 2 to the reactor and 3-5 to the feedtank. Heat the reactorcontents to 35° C. Add 50% of 3-5 to the reactor and mix for 30 minutes.Add 50% of 6, 7 and 8 to the reactor; the polymerisation will start. Letthe temperature drift to appr. 55° C. Keep at this temperature for 15minutes. Feed 50% of 9 in 30 minutes. Cool to 35° C. and repeat thisprocedure for the other 50% of the components, but now cool to 40° C.instead of 35° C. Add 10 and 11 over 30 minutes. Cool to RT.

Specifications

    ______________________________________    solids                  35-36%    pH                      8.4    viscosity (mPas @ 25° C.)                            180    sediment before sieving (%)                            <0.1%    FM (%)                  <0.1%    MFFT (°C.)       10° C.    Koenig hardness         103 sec    ______________________________________

An aqueous solution of an acid-functional oligomer OL3 lacking anymonomer for the purpose of providing subsequent covalent crosslinkingmonomer was prepared as follows:

Recipe for oligomer OL3

Composition MMA/MAA=90/10

sodium lauryl sulphate (emulsifying agent): 0.5% on TM (s/s). 25% in thereactor; 75% in the feed.

AP: 0.3% on TM (s/s). Added as a separate feed during emulsion polym.(solids of the feed is 1.5% in demin. water).

LMKT and 3MPA: 2.4% on TM

Neutralization: 1 SA NH₃

solids of the neutralized solution 25%

Logsheet and Procedure for the Preparation of OL3

    ______________________________________    Nr       Component         Amount (g)    ______________________________________    1        H.sub.2 O         911.8    2        SLS               1.8    3        AP (1.5% (s/s) in demin. water                               87.2    4        Water             188.3    5        SLS               5.5    6        LMKT              7.0    7        3MPA              3.5    8        MMA               392.4    9        MAA               43.6    10       NH.sub.3 (25%)    34.5    11       H.sub.2 O         124.4    ______________________________________

1 and 2 are charged to the reactor. 4-9 are charged to the feedtank andpreemulsified by stirring. Heat the batch to 70° C. and add 5% of thepreemulsified feed to the reactor. Heat the batch to 80° C. and add 30%of 3. Wait 5 minutes and start feeding the remainder of thepreemulsified feed over 60 minutes and simultaneously feed the remainderof 3 over 70 minutes at 85° C. Hold at 85° C. for 30 minutes and thenadd 10 and 11. Hold at 80° C. for another 20 minutes and cool to RT.

Specifications

    ______________________________________    solids                  25%    pH                      8.3    viscosity               55    sediment                <0.1%    Tg (DSC and calculated °C.)                            110° C.    Mn                      9700    d                       2.5    ______________________________________

EXAMPLE C5

In this comparative example, a composition lacking groups intended forproviding covalent crosslinking was prepared using the oligomer OL3 toinvestigate the effect on MFFT/Koenig hardness balance of ioniccrosslinking. A polybatch method was used (as with Example 4). (Thecomposition had oligomer/hydrophobic polymer Tg values in accordancewith the requirements of the invention process).

Recipe

Composition Oligomer part: (see above for OL3) Polymer part: BMA/BA=74/26 Tg polymer part, calculated (°C.)=0

Oligomer/polymer (s/s): 60/100

All oligomer in the reactor

Initiator system 0.26% t-BHPO on TM (s/s) in the reactor 0.05%i-ascorbic acid on TM (s/s) in the reactor 5.07% FeE =A on t-BHPO in thereactor 0.21% i-ascorbic acid on TM (s/s) fed into the reactor

solids: ca. 35%

Logsheet and Procedure for Preparation of Composition of Ex C5

    ______________________________________    Nr       Component        Amount (g)    ______________________________________    1        Water            198.4    2        Oligomer OL3 solution                              800    3        BMA              296    4        BA               104    5        tBHPO (30% slurry in demin.                              3.5             water)    6        Fe EDTA (1% solution*)                              5.2    7        i-ascorbic acid 1% in demin                              20.0             water    8        i-ascorbic acid 1% in demin                              84.0             water    9        Water            209.3    ______________________________________     (*see Example 3)

Charge 1 and 2 to the reactor and 3 and 4 to the feedtank. Heat to 35°C. Add 50% of 3 and 4 to the reactor and mix for 30 minutes. Add 50% of5, 6 and 7 to the reactor; the polymerisation will start. Let thetemperature drift to appr. 55° C. Keep at this temperature for 15minutes. Feed 50% of 8 in 30 minutes. Cool to 35° C. and repeat thisprocedure for the other 50% of the components, but now cool to 40° C.instead of 35° C. Add 9 over 30 minutes. Cool to RT.

Specifications

    ______________________________________    solids                 35%    pH                     8.3    MFFT (° C.)     10    Koenig hardness        80      sec    viscosity (mPas @ 25° C.)                           200    sediment (%)           <0.1%    FM (%)                 <0.1%    ______________________________________

100 g of the above latex was formulated with a mixture of 0.57 g demin.water, 0.27 g zinc oxide, 0.34 g ammonium carbonate and 0.49 g 25%ammonium hydroxide solution in water. This provides a Zn metal ioncrosslinking latex with the following values:

    ______________________________________    MFFT (° C.)     37    Koenig hardness        63 secs    ______________________________________

Thus the effect of ionic crosslinking has been to both increase MFFT andlower Koenig hardness.

Further acid-functional oligomers OL4 and OL5 in aqueous solutionpossessing covalent crosslinker functionality were prepared as follows:

Recipe for Oligomer OL4

Composition EA/MMA/DAAM/MAA=27.4/58/8/6.6 The preparative procedure wasexactly as for that of oligomer OL1 (using Surfagene FAZ 109 V asemulsifying agent etc).

Recipe for Oligomer OL5

Composition MMA/DAAM/MAA=84/6/10 The preparative procedure was exactlyas for that of oligomer OL2 (using SLS as emulsifier etc)

Logsheet and Procedure for the Preparation of the Oligomers OL4 and OL5

    ______________________________________                            OL4 Prep   OL5 Prep    Nr   Component          Amount (g) Amount (g)    ______________________________________    1    H.sub.2 O          909.7      846.2    2    Surfagene FAZ109V  3.2        --    3    AP (1.5% in demin water)                            101.8      95.5    4    SLS (sodium lauryl sulphate 30%                            --         2         solids)    5    NaHCO.sub.3        1.0        --    6    H.sub.2 O          214.9      207.1    7    MMA                295.2      402.9    8    DAAM               40.7       28.8    9    MAA                33.6       48.0    10   EA                 139.3      --    11   Surfagene FAZ109V  9.5        --    12   SLS                --         6.0    13   NaHCO.sub.3        0.5        --    14   LMKT               8.1        7.7    15   3MPA               --         3.8    16   NH.sub.3 (12.5%)   103.2      151.7    17   H.sub.2 O          39.3       0.9    ______________________________________

Charge 1, 2 and 4, 5 to the polymerisation reactor. Heat the reactorcontents to 70° C. and add 5% of the pre-emulsified feed 6-15. Heat thereactor contents to 80° C. and charge 30% of 3 to the reactor and waitfor 5 minutes. Feed the remainder of 6-15 and 3 at 85° C. over periodsof 60 minutes and 70 minutes respectively. Rinse the feedtank with 17and keep the reactor contents at 85° C. for another 30 minutes. Slowlyadd 16 to the reactor and keep at 80° C. for another 30 minutes. Theoligomer will dissolve or partly dissolve in this time. Cool down to 25°C.

Specifications for the Oligomers OL4 and OL5

    ______________________________________    solids               27-28%    pH                   10 for OL4, 10 for OL5.    viscosity (mPas at 25° C.)                         150 for OL4, 140 for OL5    sediment             <0,2%    FM                   <100 ppm    Mn                   ca.9000 for OL4,                         ca.8000 for OL5    d                    2.3-2.4    Tg for OL4 (calculated ° C.)                         60    Tg for OL5 (DSC and calculated ° C.)                         110    ______________________________________

The oligomer solutions of OL4 and OL5 were employed in the preparationof the following invention compositions of Examples 6, 7 and 8 using thepolybatch method described for Examples 4 and C5.

EXAMPLES 6, 7, and 8

Recipes

    ______________________________________    Ex 6      Composition: BMA/BA/DAAM = 74.1/22.9/3              Oligomer: OL4              Tg polymer part, calculated (° C.) = 3    Ex 7      Composition: BMA/BA/S/DAAM = 26/31/39/4              Oligomer: OL5              Tg polymer part, calculated (° C.) = 20    Ex 8      Composition: BMA/BA/S/DAAM = 46.7/10.3/39/4              Oligomer: OL5              Tg polymer part, calculated (° C.) = 39    ______________________________________

Other Procedures as for Examples 4, and C5.

Logsheet and Procedure for Preparation of Compositions of Exs 6, 7 and 8

    ______________________________________                       Ex 6 Prep Ex 7 Prep                                         Ex 8 Prep    Nr  Component      Amount (g)                                 Amount (g)                                         Amount (g)    ______________________________________     1  Water          221.6     186.0   323.5     2  oligomer OL4 solution                       829.7     --      --     3  oligomer OL5 solution                       --        809.8   809.8     4  BMA            259.8     94.8    170.2     5  BA             80.1      113.0   37.5     6  S              --        142.1   142.1     7  DAAM           10.5      14.6    14.6     8  tBHPO (30% slurry in                       3         3.1     3.1        demin water)     9  FeEDTA (1% solution)                       4.5       4.7     4.7    10  i ascorbic acid (1% in                       17.5      18.2    18.2        demin water)    11  i ascorbic acid (1% in                       73.6      76.5    76.5        demin water)    12  Water          8.0       96.6    81.4    13  ADH            13.1      12.0    12.8    ______________________________________

Charge 1-3 to the polymerisation reactor and 4-7 to the feedtank. Heatto 35° C. Add 50% of 4-7 to the reactor and mix for 30 minutes. Add 50%of 8, 9 and 10 to the reactor and the polymerisation will start. Let thetemperature drift to appr. 55° C. Keep at this temperature for 15minutes. Feed 50% of 11 in 30 minutes. Cool to 35° C. and repeat thisprocedure for the other 50% of the components, but now cool to 40° C.instead of 35° C. Add 12-13 in 30 minutes. Cool to RT.

The MFFT's and Koenig hardness values were:

    ______________________________________                Koenig    MFFT (° C.)                Hardness (sec)                           pH     Visc. (mPas @ 25° C.)    ______________________________________    Ex 6  6         100        8.3  150    Ex 7 28         132        8.2  170    Ex 8 45         157        8.4  190    ______________________________________

The specifications for sediment and FM were similar to those for Example4.

The compositions of Examples 1, 2, 3, 4, C5, 6, 7 and 8 were assessedfor water and solvent resistance using spot tests conducted in thefollowing manner:

A coating of an example is applied at 100 μm wet film thickness to atest chart (Leneta Company, Form 2C). It is allowed to dry at RT for 4hours and at 50° C. for 16 hours.

A wad of cotton wool, soaked in water or ethanol 48%, is placed on thecoating and maintained in a saturated state for 16 hours by placing aglass over the wad. The wad is removed and the coating is assessed forappearance (whitening, cracks or dissolution).

If no damage at all is observed, a number of 5 is awarded. If thecoating has completely dissolved a number of 0 is awarded. Numbers from4 to 1 stand for increasing damage to the appearance of the coating.

The spot test results for the Examples were as follows:

    ______________________________________           Ex 1   Ex 2   Ex 3 Ex 4 Ex C5 Ex 6 Ex 7 Ex 8    ______________________________________    water  5      5      5    5    3     5    5    5    ethanol           3      4      4    3    2     4    5    4    ______________________________________

It will be observed that all the invention compositions possessexcellent water resistance and reasonably good ethanol resistance. Bycontrast, the comparative composition of Example C5 has significantlypoorer water and ethanol resistance.

A further acid-functional oligomer OL6 was prepared having nocrosslinker monomer intended for effecting covalent crosslinking (in anoligomer/polymer composition) after coating formation, but havinginstead a difunctional monomer (ALMA) for effecting grafting (orprecrosslinking) during the formation of the oligomer/polymercomposition.

Recipe for Oligomer OL6

Composition BA/MMA/ALMA/MAA=34/45.4/0.5/20

SLS (emulsifying agent): 0.5% on TM (s/s)

AP: 0.3% on TM (1.5% in demin. water)

LMKT: 5.5% on TM.

neutralization: 1 SA NH₃

solids of neutralized solution: 24 %.

Logsheet and Procedure for Preparation of the Oligomer OL6

    ______________________________________    Nr      Component          Amount (g)    ______________________________________    1       H.sub.2 O          1073.3    2       AP (1.5% in demin. water)                               84.7    3       SLS (sodium lauryl sulphate, 30%                               1.8            solids)    4       H.sub.2 O          188.4    5       MMA                192.7    6       MAA                84.7    7       SLS                5.3    8       LMKT               23.2    9       NH.sub.3 (12.5%)   133.9    10      H.sub.2 O          9.1    11      BA                 144.0    12      ALMA               2.1    ______________________________________

Charge 1 and 3 to the reactor. Heat the reactor contents to 70° C. andadd 5% of the pre-emulsified feed 4-8. Heat the reactor contents to 80°C. and charge 30% of 2 to the reactor and wait for 5 minutes. Startfeeding, with the reactor contents at 85° C., 4-7 and 11, 12 over aperiod of 60 minutes and 2 over a period of 70 minutes. Rinse thefeedtank with 10 and keep the reactor contents at 85° C. for another 30minutes. Slowly add 9 to the reactor and keep at 80° C. for another 30minutes. The oligomer will dissolve in this time. Cool down to 25° C.

Specifications

    ______________________________________    solids                24%    pH                    8.4    viscosity (mPas)      >1000    sediment              <0,2%    FM                    <100    ppm    Tg (DSC and calculated ° C.)                          49    ______________________________________

EXAMPLE C9

In this comparative example, a polymer composition is prepared using theoligomer OL6 in order to yield a product with grafting(pre-crosslinking) between the oligomer and polymer phases in theresulting emulsion composition (i.e. as in the preferred process of EP0,587,333). A polybatch procedure was used. (The composition hadoligomer/hydrophobic Tg polymer values in accordance with therequirements of the invention process).

Recipe

    ______________________________________    Composition    ______________________________________    Oligomer part       OL6    Polymer part        BA = 100% (homopolymer)    Tg polymer part, (° C.)                        -45    oligomer/polymer (s/s)                        = 100/100    Initiator system    0.26% tBHPO on TM (s/s) in the reactor    0.05% i-ascorbic acid on TM    (s/s) in the reactor    5.07% FeEDTA on tBHPO (s/s)    in the reactor    0.21% i-ascorbic acid on TM    (s/s) fed into the reactor    all oligomer in reactor    solids 30%    ______________________________________

Logsheet and Procedure for Preparation of Example C9

    ______________________________________    Nr     Component           Amount (g)    ______________________________________    1      Water               275.9    2      Oligomer OL6 solution                               897.6    3      BA                  224.4    4      tBHPO (30% slurry in demin water)                               2.0    5      FeEDTA (1% solution)                               3.0    6      i ascorbic acid 1% in demin water                               11.0    7      i ascorbic acid 1% in demin water                               47.2    8      Water               38.9    ______________________________________

Charge 1 and 2 to the reactor and 3 to the feedtank. Heat the reactorcontents to 35° C. Add 50% of 4, 5 and 6 to the reactor and thepolymerisation will start. Let the temperature drift to appr. 55° C.Keep at this temperature for 15 minutes. Feed 50% of 7 in 3 minutes.Cool to 35° C. and repeat this procedure for the other 50% of thecomponents, but now cool to 40° C. instead of 35° C. Add 8 in 30minutes. Cool to RT.

Specifications

    ______________________________________    solids                30%    pH                    8.4    MFFT (° C.)    0    Koenig Hardness       29      sec    viscosity (mPas @ 25° C.)                          >1000    sediment (%)          <0.2%    FM (%)                <100    ppm    ______________________________________

EXAMPLES C10 AND C11

In these comparative examples, oligomer/hydrophobic polymer compositionsare prepared in which the oligomer is solubilized by neutralization inthe aqueous phase subsequent to the polymerisation to form thehydrophobic polymer (instead of before effecting this polymerisation--asin all the preceding examples), this being the preferred technique of EP0,587,333 to effect solubilization. In Example C11, the monomer systemcontains no monomer intended for covalent crosslinking while in ExampleC10, the monomer system does include such crosslinker monomer (i.e. asper the present invention but solubilizing the oligomer afterpolymerisation instead of before polymerisation to form the hydrophobicpolymer). (Both compositions had oligomer/hydrophobic polymer Tg valuesin accordance with the requirements of the invention process).

Recipe for Example C10

Oligomer phase composition EA/MMA/DAAM/MAA=12.1/73.3/8/6.6 Tg (DSC andcalculated °C.): 85

Polymer phase composition BMA/BA/DAAM=74/1/22.9/3 Tg (DSC and calculated°C.): 3

0.5 SLS (s/s) on TM used as the surfactant. 0.3 AP (1.5% solution indemin. water) used as a separate initiator feed for both phases

oligomer/polymer (s/s): 60/100

Recipe for Example C11

oligomer phase composition EA/MMA/MAA=12.1/81.3/6.6 Tg (DSC andcalculated °C.): 88

Polymer phase composition BMA/BA=75.6/24.4 Tg (calculated °C.): 1 Tg(DSC °C.): 0 Otherwise identical with Example C10

Logsheet and Procedure for Examples C10 and C11

    ______________________________________                           Ex C10     Ex C11    Nr    Component        Amount (g) Amount (g)    ______________________________________    1     water            800.4      800.4    2     SLS (30% solids) 2.2        2.2    3     AP (1,5% in demin. water)                           131.3      131.3    4     water            102.9      102.9    5     SLS (30% solids) 3.3        3.3    6     LMKT             14.8       14.8    7     EA               28.6       28.6    8     MMA              173.3      192.2    9     DAAM             18.9       --    10    MAA              15.6       15.6    11    BMA              311.4      317.7    12    BA               96.2       102.5    13    DAAM             12.6       --    14    water            90.0       90.0    15    ADH              14.6       --    16    NH.sub.3 (12.5%) 42.4       42.4    ______________________________________

Charge 1 and 2 to the polymerisation reactor and heat to 85° C.Pre-emulsify 4-10 and charge 10% to the reactor. Then charge 20% of 3 tothe reactor and wait for 5 minutes. Charge the remainder of the feed(4-10) in 50 minutes and charge 40% of 3 over a period of 60 minutes at85%. This forms the oligomer. Charge 11-13 to the feed tank and feedthis to the reactor in an additional 50 minutes. Simultaneously chargethe remainder of 3 to the reactor over a period of 60 minutes at 85° C.Keep at 85° C. for another 30 minutes. This forms the hydrophobicpolymer. Then slowly charge 16 to the reactor and wait for another 30minutes. Cool to 25° C. and add 15 to the reactor (Example C10 only);rinse with 14.

Specifications:

    ______________________________________    pH                 9-10    solids            37-38%    viscosity (mPas at 25° C.)                      1500 for Ex C10, 1570 for Ex C11    FM                <100 ppm    sediment          <0.2%    MFFT (° C.)                      0 for Ex C10, 37 for Ex C11    Koenig hardness   52 sec for Ex C10, 13 sec for                      Ex C11    ______________________________________

The water and ethanol resistances of the compositions of Examples C9,C10 and C11 were assessed (procedure described supra). These were asfollows (the values for MFFT and Koenig hardness, given above, are alsoincluded):

    ______________________________________             Ex C9      Ex C10  Ex C11    ______________________________________    MFFT ° C.               0            0       37    hardness (sec)               29           52      13    water resist.               4            3        5    ethanol resist.               0            2        0    ______________________________________

It will be noted that the properties of the post neutralization ExampleC10 with crosslinking are extremely poor compared with those of theinvention examples, both in terms of MFFT/Koenig hardness balance andwater/ethanol resistance. The properties of the post neutralizationExample C11 without crosslinking gives an even worse MFFT/Koenighardness balance and very poor ethanol resistance. The properties of thegrafting (or pre-crosslinking) Example C9 are also very poor in terms ofMFFT/Koenig hardness balance and ethanol resistance.

We claim:
 1. Process for the production of an organic solvent-freeaqueous crosslinkable polymer composition useful for coating, whichprocess is organic solvent-free and comprises:a) preparing an aqueoussolution of an acid-functional oligomer built from olefinicallyunsaturated monomers, said oligomer having a number average molecularweight Mn within the range of from 500 to 50,000 and a glass transitiontemperature (Tg) within the range of 10 to 125° C., said oligomer beingformed using an organic solvent-free aqueous emulsion or aqueoussolution polymerisation process, and said acid functionality by itselfor by neutralization rendering the oligomer water-soluble, and saidoligomer also having crosslinker functional groups for impartingcrosslinkability when the aqueous polymer composition is subsequentlydried, b) conducting an aqueous emulsion polymerisation process to forman aqueous emulsion of a hydrophobic polymer from at least oneolefinically unsaturated monomer in the presence of the aqueous solutionof the oligomer, said hydrophobic polymer having a Tg which is at least40° C. below the Tg of said oligomer, and said hydrophobic polymeroptionally having crosslinker functional groups for impartingcrosslinkability when the aqueous polymer composition is subsequentlydried, and c) combining the aqueous emulsion from b) with a crosslinkingagent by addition of the crosslinking agent after the polymerisation instep b) and/or performing the polymerisation in the presence of thecrosslinking agent, said crosslinking agent being reactable with thecrosslinker functional groups of the oligomer and (if present) of thehydrophobic polymer on subsequent drying to effect crosslinking, whereinsaid crosslinking agent is not an agent which effects crosslinking bythe formation of ionic bonds,and wherein further, said polymercomposition on drying has a Koenig hardness of at least 40 sec and saidpolymer composition has a minimum film forming temperature of ≦55° C. 2.Process according to claim 1 wherein said oligomer has a number averagemolecular weight of from 2,000 to 25,000.
 3. Process according to claim1 wherein said oligomer has a Tg within the range of from 50 to 125° C.4. Process according to claim 3 wherein said oligomer has a Tg withinthe range of from 70 to 125° C.
 5. Process according to claim 1 whereinsaid polymer composition on drying has a Koenig hardness of from 60 to200 secs.
 6. Process according to claim 1 wherein said polymercomposition has a minimum film forming temperature of from 0 to 55° C.7. Process according to claim 6 wherein said polymer composition has aminimum film forming temperature of from 0 to 30° C.
 8. Processaccording to claim 1 wherein the resulting composition has Koenighardness and minimum film forming temperature according to the followingempirical relationship:

    H≧1.5T+70

where H is Koenig hardness in seconds and T is minimum film formingtemperature in °C.
 9. Process according to claim 8 wherein the empiricalrelationship is:

    H≧1.5T+90.


10. Process according to claim 1 wherein said oligomer is completely orpartially, dissolved in the aqueous medium in step a).
 11. Processaccording to claim 10 wherein dissolution of the oligomer is effected byneutralization of the acid groups thereof using a base.
 12. Processaccording to claim 1 wherein said oligomer is derived from anolefinically unsaturated monomer system which includes an acid-bearingcomonomer(s), or a comonomer(s) bearing an acid-forming group whichyields, or is subsequently convertible to, such an acid group, and acomonomer(s) which has functional groups for imparting crosslinkability.13. Process according to claim 12 wherein the acid bearing monomer(s) isselected from the group consisting of carboxyl-containing olefinicallyunsaturated monomers.
 14. Process according to claim 13 wherein themonomer(s) is selected from the group consisting of carboxyl-functionalacrylic monomers.
 15. Process according to claim 14 wherein saidcarboxyl bearing monomer(s) is selected from the group consisting ofacrylic acid, methacrylic acid, itaconic acid and fumaric acid. 16.Process according to claim 12 wherein said monomer system from which theoligomer is formed includes a non-acid functional non-crosslinkingcomonomer(s) selected from the group consisting of acrylate andmethacrylate esters; styrenes, dienes, vinyl esters, nitriles, andolefinically unsaturated halides.
 17. Process according to claim 16wherein said non-acid functional non-crosslinking comonomer(s) isselected from the group consisting of methyl acrylate, ethyl acrylate,n-butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethylmethacrylate, n-butyl methacrylate, isobornyl acrylate or methacrylate,cyclohexyl acrylate or methacrylate, styrene, alpha-methyl styrene,t-butylstyrene, acrylonitrile, methacrylonitrile, vinyl chloride,vinylidene chloride, vinyl fluoride, vinyl acetate, isoprene and1,3-butadiene.
 18. Process according to claim 12 wherein the functionalgroups for providing crosslinkability are selected from the groupconsisting of epoxy, hydroxyl, ketone and aldehyde, groups.
 19. Processaccording to claim 12 wherein said comonomer(s) with functional groupsfor imparting crosslinkability is (are) selected from the groupconsisting of glycidyl acrylate or methacrylate, hydroxyethylmethacrylate or acrylate, acrolein, methacrolein, methyl vinyl ketone,acetoacetoxyethyl methacrylate or acrylate and diacetone acrylamide. 20.Process according to claim 12 wherein the acid-functional oligomer isderived from a monomer system comprising 1 to 45 weight % ofacid-functional comonomer(s), 0.5 to 20 weight % of crosslinkingcomonomer (s) and 98.5 to 50 weight % of non-acid functional,non-crosslinking comonomer(s).
 21. Process according to claim 20 whereinsaid oligomer is derived from a monomer system comprising 3 to 30 weight% of acid-functional comonomer(s), 1 to 15 weight % of crosslinkingcomonomer(s) and 96 to 65 weight % of non-acid functional,non-crosslinking comonomer(s).
 22. Process according to claim 20 whereinthe acid comonomer(s) is methacrylic acid and/or acrylic acid and thenon-acid functional, non-crosslinking comonomer(s) is one or moreselected from the group consisting of methyl methacrylate, styrene,ethylacrylate, n-butyl methacrylate and n-butyl acrylate.
 23. Processaccording to claim 20 wherein said oligomer is derived from a monomersystem which comprises 3 to 12 weight % of methacrylic acid and/oracrylic acid, 1 to 10 weight % of diacetone acrylamide and/oracetoacetoxyethyl methacrylate, 50 to 90 weight % of methylmethacrylate, 0 to 30 weight % of one or more of ethyl acrylate, n-butylacrylate or n-butyl methacrylate and 0 to 40 weight % of styrene. 24.Process according to claim 1 wherein the aqueous emulsion polymerisationof step b) is performed using an amount of emulsifying agent(s) newlyadded for that step (excluding the oligomer) which is less than 0.5weight % based on the total weight of monomers charged for step b). 25.Process according to claim 1 wherein the only emulsifying agent(s) whichmay be present (excluding the oligomer itself) is that remaining fromthe emulsifying agent(s) used in the oligomer polymerisation of step a).26. Process according to claim 1 wherein the oligomer formed in step a)acts as an emulsifying agent in the polymerisation of step b). 27.Process according to claim 1 wherein the polymerisation processes insteps a) and b) are carried out in the same polymerisation vessel. 28.Process according to claim 1 wherein said hydrophobic polymer is derivedfrom an olefinically unsaturated monomer system which includes anon-acid bearing, non-crosslink monomer(s).
 29. Process according toclaim 28 wherein said non-acid, non-crosslinking monomer(s) is selectedfrom the group consisting of one or more of acrylate and methacrylateesters, styrenes, dienes, vinyl esters, nitriles, vinyl halides andvinylidene halides.
 30. Process according to claim 29 wherein theacrylate and methacrylate esters are normal and branched alkyl esters ofC1 to C12 alcohols, the styrenes are styrene, α-methyl styrene, o-, m-and p- methylstyrene, o-, m- and p-ethyl styrene, p-chlorostyrene, andp-bromostyrene, the dienes are 1,3-butadiene and isoprene, the vinylester is vinyl acetate, the vinyl halide is vinyl chloride, and thevinylidene halide is vinylidene chloride.
 31. Process according to claim28 wherein the monomer system used in the preparation of the hydrophobicpolymer includes a crosslinking comonomer(s) having a functionalgroup(s) for providing crosslinkability selected from the groupconsisting of epoxy, hydroxy, ketone and aldehyde groups.
 32. Processaccording to claim 31 wherein said crosslinking comonomers(s) is one ormore selected from the group consisting of glycidyl methacrylate oracrylate, hydroxyethyl methacrylate or acrylate, acetoacetoxymethacrylate or acrylate and diacetone acrylamide.
 33. Process accordingto claim 28 wherein the monomer system used for the preparation of thehydrophobic polymer contains less than 5 weight % of any acid-functionalcomonomer.
 34. Process according to claim 33 wherein the monomer systemcontains no acid-functional comonomer.
 35. Process according to claim 1wherein said hydrophobic polymer is made from a monomer systemcomprising at least one selected from the group consisting of C1-C10alkyl methacrylates and C3-C10 alkyl acrylates, and diacetone acrylamideand/or acetoacetoxyethyl methacrylate.
 36. Process according to claim 1wherein said hydrophobic polymer has a number average molecular weightof at least 50,000.
 37. Process according to claim 36 wherein thehydrophobic polymer has a number average molecular weight of at least100,000.
 38. Process according to claim 1 wherein the aqueous solutionof the oligomer of step a) is admixed with all of the monomers to beused in the formation of the hydrophobic polymer and an otherwiseconventional "all-in-one" batch polymerisation (with no further additionof monomer(s)) is carried out to make the hydrophobic polymer. 39.Process according to claim 1 wherein all of the oligomer solution ofstep a) is present in the polymerisation vessel used to make thehydrophobic polymer prior to the start of polymerisation together withsome of the monomer system for the hydrophobic polymer, with theremainder of the monomer system for the hydrophobic polymer being addedin one addition after the polymerisation has commenced.
 40. Processaccording to claim 1 wherein all of the oligomer solution of step a) ispresent in the polymerisation vessel used to make the hydrophobicpolymer prior to the start of the polymerisation, and the monomer systemfor the hydrophobic polymer is split into several equal parts (batches),these parts being added and polymerised consecutive to one another. 41.Process according to claim 1 wherein part (or none) of the monomersystem for the hydrophobic polymer is present prior to the start ofpolymerisation in the polymerisation vessel used to make the hydrophobicpolymer and part (or the entire amount) is fed to the reaction medium inthe polymerisation vessel during the course of polymerisation. 42.Process according to claim 41 wherein the aqueous oligomer solution ofstep a) is present in part in the reaction medium for the polymerisationto make the hydrophobic polymer while part of the aqueous oligomersolution is mixed with the entire monomer system for the hydrophobicpolymer and the latter fed to the reaction medium in the polymerisationvessel during the polymerisation.
 43. Process according to claim 41wherein the entire oligomer solution of step a) is present in thepolymerisation vessel prior to the start of polymerisation and theentire monomer system for the hydrophobic polymer is fed to the vesselduring the polymerisation, there being no oligomer present in themonomer feed.
 44. Process according to claim 41 wherein all of theaqueous oligomer solution of step a) is present in the polymerisationvessel prior to the start of the polymerisation together with part ofthe monomer system for the hydrophobic polymer, and the remainder of themonomer system for the hydrophobic polymer fed during polymerisation,there being no oligomer in the feed.
 45. Process according to claim 41wherein part of the oligomer solution of step a) is present in thepolymerisation vessel prior to start of the polymerisation to make thehydrophobic polymer together with part of the monomer system for thehydrophobic polymer, and the remainder of the monomer system for thehydrophobic polymer admixed with the remainder of the oligomer solutionis fed during polymerisation.
 46. Process according to claim 1 whereinthe crosslinking agent is selected, depending on the crosslinkingfunctionality in the oligomer and (if present) in the hydrophobicpolymer, from the group consisting of a polyisocyanate, melamine,glycoluril, a polyamine, and a polyhydrazide.
 47. Process according toclaim 1 wherein the ratio of the number of crosslinker groups present inthe oligomer and (if employed) in the hydrophobic polymer to the numberof reactive groups (for crosslinking purposes) in the crosslinking agentis within the range of from 10/1 to 1/3.
 48. Process according to claim1 wherein the solids content of the resulting aqueous composition iswithin the range of from 20 to 65 wt % on a total weight basis. 49.Process according to claim 1 wherein the relative amounts of theoligomer and the hydrophobic polymer in the resulting aqueouscomposition is such that the wt % of the oligomer, based on the wt ofthe oligomer plus the hydrophobic polymer, is within the range of from 1to 70 wt %.
 50. Aqueous crosslinkable polymer composition which isorganic solvent-free and is useful for coating, which composition isproduced by a process which is organic solvent-free and comprises:a)preparing an aqueous solution of an acid-functional oligomer built fromolefinically unsaturated monomers, said oligomer having a number averagemolecular weight Mn within the range of from 500 to 50,000 and a glasstransition temperature (Tg) within the range of 10 to 125° C., saidoligomer being formed using an organic solvent-free aqueous emulsion oraqueous solution polymerisation process, and said acid functionality byitself or by neutralization rendering the oligomer water-soluble, andsaid oligomer also having crosslinker functional groups for impartingcrosslinkability when the aqueous polymer composition is subsequentlydried, b) conducting an aqueous emulsion polymerisation process to forman aqueous emulsion of a hydrophobic polymer from at least oneolefinically unsaturated monomer in the presence of the aqueous solutionof the oligomer, said hydrophobic polymer having a Tg which is at least40° C. below the Tg of said oligomer, and said hydrophobic polymeroptionally having crosslinker functional groups for impartingcrosslinkability when the aqueous polymer composition is subsequentlydried, and c) combining the aqueous emulsion from b) with a crosslinkingagent by addition of the crosslinking agent after the polymerisation instep b) and/or performing the polymerisation in the presence of thecrosslinking agent, said crosslinking agent being reactable with thecrosslinker functional groups of the oligomer and (if present) of thehydrophobic polymer on subsequent drying to effect crosslinking, whereinsaid crosslinking agent is not an agent which effects crosslinking bythe formation of ionic bonds,and wherein further, said polymercomposition on drying has a Koenig hardness of at least 40 sec and saidpolymer composition has a minimum film forming temperature of ≦55° C.51. Composition according to claim 50 wherein said composition hasKoenig hardness and minimum film forming temperature according to thefollowing empirical relationship:

    H≧1.5T+70

where H is Koenig hardness in seconds and T is minimum film formingtemperature in °C.
 52. Composition according to claim 51 wherein theempirical relationship is:

    H≧1.5T+90.


53. A film, polish, varnish, lacquer, paint, ink or adhesive comprisinga composition according to claim
 50. 54. a composition according toclaim 50 deposited as a protective coating on a wood, plastic, paper ormetal substrate.